Just after the winter test of the large range of electric vehicles, we ran all the way to the photoelectric lying in the nest. Gain a deeper understanding of the circumstances under which electric vehicles consume the most electricity. After the test, on the return trip from Hefei to Shanghai, I led the C11, choosing the right lane most of the time and slowly cruising at a speed of about 100km/h. Most of the electric cars of other peers on the road have surpassed me... I wasn't driving a car, but I was too sensitive to the condition of the car. Although I drive a cost-effective fuel car, I also drive at a speed limit of 120km/h, but driving an electric car, running to 120km/h is very uncomfortable: I feel the electric motor running with my breath held. I've been working in a state of overdrive. The NVH performance in the car also plummeted. It doesn't feel like a small displacement 3-cylinder fuel engine spinning at high speed. In fact, whether it is cruising at a speed of 100km/h or too high, you can feel that electric vehicles are more comfortable running 80km/h.
Comfort, on the other hand, is mainly power consumption. The faster the speed, the power consumption of electric vehicles will skyrocket! It has been calculated that the time saved by running 120km/h will go back to the time spent on excess use when charging in the service area. Taking the zero-run C11 as an example, (in fact, all electric vehicles are like this) even if it cruises at a speed of 100km/h, it will not become higher, and the power consumption is about 19~20kWh/100km. However, if you run 120km/h, the power consumption will increase to about 26kwh/100km. But there was a car called the Porsche Taycan. Even driving the entry-level 408-horsepower Taycan cruising on the highway is still more comfortable than many electric cars, and if it is not too low body and car weight, the Taycan and fuel vehicles are not much different. Because the Porsche Taycan has a gearbox. In the world of electric cars, only the Porsche Taycan has a 2-speed gearbox on the rear axle, but porsche purposes are mainly for performance, the Taycan with the gearbox to break through 250km/h (the entry version is 230km/h). Let's talk about transmissions for electric cars.
Electric vehicles are thought to require transmissions. The speed of the motor can be used over a very wide range to bring the maximum speed to 16000 rpm, so the motor only needs to adjust the input current to control its power output. Maximum torque can be generated at the moment of the start of the motor, and it is possible every second for the city to start, without the need for a transmission to carry out the acceleration required for daily operation. Therefore, electric vehicles only need to install a single reducer, and the power transmission from the electric motor to the wheel can be completed through the axle. However, as we started the test ride experience in our article, although the electric motor without transmission can travel to extreme speeds of more than 120km/h, it rises to a maximum speed of 13000rpm at high speed cruising, and the entire NVH, power performance, and efficiency are very low. That's why electric cars are very power-hungry when driving on highways. With the transmission, the speed of the motor can be controlled in the most effective range (about 7000 ~ 9000rpm) during high-speed cruising, and the NVH and comfort are improved, not only the speed is high, but also the endurance distance when driving at high speed will also increase.
In fact, not only at high speed cruising, but also in the electric vehicle starting, accelerating, low-speed climbing steep slopes, the motor will also run inefficiently for a long time, when the temperature of the power consumption itself will be too high. The intervention of the transmission will increase the range of traffic jam cities, or mountain cities such as Chongqing. In fact, it is not only luxury goods such as porsche Taycan, parts supplier Bosch launched a CVT gearbox for electric vehicles in 2019. At that time, we had another test ride experience. This is how the engineers who entered the Ph.D. answered questions about electric vehicle transmissions. Won't adding CVT to electric vehicles increase body weight? In addition, if you add the possible increase in mechanical loss, will the loss be compensated? Increasing the transmission equals increasing the cost. Bosch engineers explain. First of all, the structure of this electric vehicle CVT is simpler than that of traditional fuel vehicles, and its size is smaller. In terms of cost, the E-car CVT thing is only about half that of a fuel vehicle. Although the CVT transmission was added, due to Bosch's improved efficiency, the main engine factory adopted a smaller power motor on the basis of achieving the same power performance and endurance distance as before, and calculated that the battery pack could also be used to be smaller. This completely counteracts the weight problems caused by the increase in CVT.
What about cost? Bosch also believes that the use of CVT gearboxes will increase costs, and OEMs can offset costs by replacing smaller power motors and battery packs. CVT to improve the vehicle's dynamics and comfort to improve product power is also worth it. We were driving a test car with a CVT transmission for electric vehicles. If you drive a test car equipped with a CVT, you will find that although it is no longer so "aggressive" at the beginning, the acceleration is still very strong, fast, and more flexible, a bit closer to the performance of more advanced electric vehicles. More obviously, after the speed exceeded 60km/h, the linear acceleration did not recover very quickly as before, but maintained very well. While improving the operation quality of electric vehicles, the energy consumption of electric vehicles at high speeds is greatly reduced. Therefore, with the advancement of technology, the special transmission for electric vehicles with simple structure and controllable cost has become a development trend.